In a liquid crystal display device, cold cathode fluorescent tubes are generally used as a light source of a backlight module. The color reproduction range of a backlight module using cold cathode fluorescent tubes is only 70%˜85% of the color reproduction range of a cathode ray tube (CRT). It is difficult to reproduce the high quality image for the liquid crystal display device. Therefore, various light sources have been studied to produce a wide reproduction color range. The backlight module using multiple colors (i.e., red, green, blue) light emitting diodes (LEDs) can increase the color reproduction range to 100%. But the lifetimes of different color LEDs are different from each other, it will result in the non-uniform color distribution of a backlight module after a period of use. A light source should have a stable wavelength and light intensity to improve the color reproduction range and non-uniform color distribution.